bore" or "full bore" as indicated, and show location
of each on drawings.
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API Spec 6D, ANSI Class 150, [reduced bore] [or] [full bore] [as
indicated]. [Minimum reduced bore size shall be 55 percent of nominal pipe
size.] [Conform to fire test requirements of API Std 607.] Provide
nonlubricated double seated type capable of handling two-way shutoff, with
weather-proof worm-gear operators, except valves 150 mm 6 inches and
smaller may be lever operated with 10 positions or infinitely adjustable
positions between full open and full close. Balls in valve sizes 350 mm 14
inches and larger shall have trunnion type support bearings. Valves in
carbon steel piping shall have steel bodies with chromium-plated or
nickel-plated steel balls. Valves in stainless steel piping and aluminum
piping shall have Type 316 stainless steel bodies and balls. Valves shall
have stainless steel stems and trim, and Viton or Teflon seats, body seals,
and stem seals. [Provide body cavity drain and factory installed drain
valve.]
2.13.3
Plug (Double Block and Bleed) Valves
API Spec 6D and MIL-V-12003 Type III, ANSI Class 150, nonlubricated,
resilient, double seated, tapered lift, plug type capable of handling
two-way shutoff; steel body, chrome-plated interior, and tapered plug of
steel or ductile iron, chrome or nickel plated, supported on upper and
lower trunnions, and steel or ductile iron, sealing slips, with Viton
seals. Valve design shall permit sealing slips to be replaced from the
bottom with the valve mounted in the piping. Valves shall operate from
fully open to fully closed by rotation of the handwheel to lift and turn
the plug. Valves shall have weatherproof operators with mechanical
position indicators and a minimum bore size of 65 percent of nominal pipe
size, unless the manufacturer can show an equivalent or greater flow rate
with a lower percent percent internal cross sectional area.
2.13.3.1
Valve Operation
Rotation of the handwheel toward open shall lift the plug without wiping
the seals and retract the sealing slips so that clearance is maintained
between the sealing slips and the valve body. Rotation of the handwheel
toward closed shall lower the plug after the sealing slips are aligned with
the valve body and force the sealing slips against the valve body for
positive closure. When valve is closed, the slips shall form a secondary
fire-safe metal-to-metal seat on both sides of the resilient seal.
2.13.3.2
Relief Valves
ANSI Class 150, steel body. Provide plug valves with automatic thermal
relief valves to relieve the pressure buildup in the internal body cavity
when the plug valve is closed. Relief valves shall open at 175 kPa 25 psi
differential pressure, and discharge to the throat of and to the upstream
side of the plug valve.
2.13.3.3
Bleed Valves
ANSI Class 150, steel body valve. Provide manually operated bleed valves
that can be opened to verify that plug valves are not leaking when in the
closed position. Provide discharge piping so that released liquid can be
contained.
SECTION 15194N
Page 19
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